The invention relates to an automatic device for application to motor vehicles, which is designed to detect and indicate any sudden deceleration of the vehicle to which it is fitted.
Currently, the driver of a motor vehicle utilizes stop lights in order to give evidence of having applied the brakes, and to indicate having finally brought the vehicle to a standstill. Upon depressing the brake pedal, the stop lamps light up when the pedal itself engages a spring-loaded switch that completes the electrical stop light circuit. In other situations, such as a reduction in road speed, application of the hand brake, changing down from high to lower gear ratios, encountering a sudden change in gradient, momentary pauses, or stalling of the engine while on the move, no visual evidence of deceleration is provided by the stop lights. Any one of these contingencies can arise in traffic, potentialy when vehicles are moving at considerable speed. Under these circumstances, drivers have no immediate warning of what is happening ahead. It often occurs that a driver will run into the back of the vehicle in front, through lack of sufficient braking distance, causing a pile-up.
In freeway driving, where speeds are higher, the situations mentioned produce a great many accidents. The situation is worsened if traffic is running in snow and ice, since application of the brakes or rapid movement down through the gears will tend to lock the wheels, causing the vehicle to skid and veer out of control.
Other factors aggravate the situation, for example, fog, in disposition of the driver during an accident (shock, fainting), and failure of the indication system, whether mechanical, hydraulic or electrical, etc.
The problem in question has existed for some time, and efforts have been made by those skilled in the art to solve it using electromechanical devices to exploit physical principles, but without any particular success.
Certain devices, for example, are operated by a mechanical pendulum, or centrifugal weights. These, however, are naturally influenced by pitching and rolling of the vehicle when in transit, by heavy articles carried in the trunk, stresses attributable to bumps in the road, vibration, and gradients.
Such is the case with devices disclosed in two patents, Great Britain 20 653 447A and U.S. Pat. No. 4,320,384, which feature the use of a mechanical pendulum in conjunction with a photocell, and German 3 313 678A1, which discloses a pendulum operating in parallel with the stop light switch.
In the particular instance of devices that use centrifugal weights, U.S. Pat. No. 3,794,971 discloses means for sensing the speed of a vehicle which is triggered by the field emitted from permanent magnets associated directly with a device designed to produce movement that is proportional to the speed of the vehicle. More exactly, the device features a combination of electrical and mechanical expedients, such that the speed of the vehicle registers by way of a cable (e.g., the speedometer drive cable) which rotates a spindle carrying two centrifugal weights. These weights impart a force to a sleeve and a lever which is proportional to the speed of the vehicle. The movement of magnets, rigidly attached to the lever, creates a variable magnetic field that excites induction transducers connected electrically to the indication medium.
Other devices are applied to parts of the engine such as the throttle flap of the carburetor, as in French 2 225 007. Others utilize a signal taken off the primary winding of the ignition coil and are triggered by a drop in speed, as in U.S. Pat. No. 4,097,842.
There are also devices, such as that disclosed in French 2 199 592, which make use of electronic devices to indicate deceleration of the vehicle. The French Patent in question comprises unspecified means which are capable of generating signals proportional to the vehicle speed, and relaying them to comparators. The comparators process the signals and compare them with a given reference. The drawings accompanying the French specification show general or block diagrams of the device only, without giving details of the single elements, so that the choice of the electric and electronic components making up each block remains undetermined.
Accordingly, the object of the invention is to overcome the drawbacks mentioned above, and in particular, to ensure that the stop lights of the vehicle indicate deceleration in real time, or before the moment when the pedal-operated stop light switch is actuated by applying the brakes.
The stated object is realized with an automatic device according to the invention, which operates independently of and in parallel with the standard stop light circuit of the vehicle, and is capable of completing a circuit in real time, thereby making traffic conditions safer.
Moreover, the device is not influenced either by pitching and rolling of the vehicle when in movement (ascent, descent, heavy loading), or by the bumpiness of the ride.